You will need to set it so you will not spawn back to the race when you get lost. You can change this in options in the main menu.

Golden Flag #1 - It is in the drip tray.

Golden Flag #2 - Keep going around untill you are on the table, drive off of it and it right by the trash can you will see it.

Golden Flag #3 - Keep driving around and you will see the third under a bench seat in the corner.

Golden Flag #4 - Go back a little and you will see a ramp leading up to the 4th flag.

Golden Flag #5 - Go back down the ramp and you will see that the floor is elevated to your right. Keep following it around until you see a small ramp you can go up and it is to your right behind where the column was.